204 DISEASES DUE TO INTERNAL PARASITES. 



cover from this stage there will be an apparent improvement in 

 its health for a few weeks time, till the gradual enlargement of 

 the cyst or cysts so press upon the brain substance as to interfere 

 with its blood supply, causing absorption of brain tissue, at the 

 same time numerous heads are protruded from the cyst, which 

 also tend to produce irritation of the brain. At the commence- 

 ment of the second stage the animal is weak and fallen away in 

 flesh, due to the first attack. This condition speedily becomes 

 aggravated, the sheep stops feeding, the appetite is lost and 

 rumination suspended. The animal has a haggard appearance, 

 due to blindness, which may affect one or both eyes, caused from 

 pressure on the optic nerve. The sheep continually moves in a 

 circle, assuming peculiar gaits and positions, depending on the part 

 of brain in which the hydatid is located. Spooner states that if 

 the head is held constantly on one side, and the animal always 

 moves in a circle, corresponding to the way the head is held, that 

 the coenurus is located in the depressed side, probably In the 

 lateral ventricle of the brain. Should the sheep move in a circle 

 sometimes in one direction, and again in another, it may be con- 

 cluded that a parasite is present in both hemispheres, and if the 

 animal depresses its head, moving forward in a straight line, 

 stumbling over and running into everything in its path, the 

 hydatid is probably located in the division of the brain between 

 the hemispheres. Again should the sheep throw up its head, 

 moving forward with a reeling motion, the conclusion is drawn 

 that the cyst is in the cerebellum or fourth ventricle of the brain. 

 When more than one cyst is present, the symptoms are a com- 

 bination of the above, and cannot be relied on as a guide for 

 operation, of which we shall treat later. When the coenurus in- 

 vades the spinal cord or medulla oblongata it causes paralysis, 

 and should this symptom be combined with blindness, the prob- 

 ability is that the cyst is located at the base of the brain. When 

 the spinal cord is invaded the sheep stagger and walk without 



